Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

202
FXUS63 KLOT 082334
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
534 PM CST Thu Jan 8 2026

.KEY MESSAGES...

- Showers and some thunderstorms are expected for areas around
  and southeast of a La Salle to Chicago line early this
  evening. Some of these storms have the potential to become
  severe with primarily damaging winds southeast of a Pontiac to
  Gary line mid-evening.

- A windy stretch of weather is expected through Friday morning,
  with frequent gusts of 35 mph. Gusts may briefly reach 50 mph
  late tonight through around daybreak Friday.

- Another storm system will deliver a round of snow and rain,
  blustery winds, and falling temperatures Saturday through
  Sunday morning.

&&

.DISCUSSION...
Issued at 254 PM CST Thu Jan 8 2026

Through Friday:

An expansive mid-latitude cyclone across the central CONUS will
bring periods of convection and strong synoptic winds to the
area late this afternoon through Friday morning. Robust WAA and
low-level moisture advection are already well underway across
the mid-Mississippi River Valley in response to an impressive
kinematic field highlighted by a strengthening 140 knot upper-
level jet nearing the area. The associated 991 hPa surface low
currently over northwest Missouri will track northeastward to
near Green Bay late tonight. Meanwhile, a somewhat sheared mid-
level trough will brush the area to the northwest overnight.

Rain/Convection: Rapid low-level saturation within modest
isentropic ascent has spread an axis of rain over much of
northern Illinois this afternoon, with a current upstream gap in
precip expected to slowly fill in over the next few hours.
However, an active area of convection over Oklahoma this morning
continues to quickly track northeastward across Missouri this
afternoon in response to an axis of enhanced low-level
convergence and slightly steeper mid-level lapse rates. The
rapid transport of low-level moisture northeastward across
Illinois through early evening will further steepen mid-level
lapse rates and promote an elongated axis of convection along
and southeast of a La Salle to Chicago line roughly in the 5-8pm
window. Much of this initial convection should remain elevated
(LPL around 900 hpa) over northern Illinois, including much of
the Chicago metro. However, focus for any severe convection will
turn to areas primarily southeast of a Pontiac to Gary line
(and especially the far southeast CWA), in the 7-11pm window
when convection has the potential to become surface-based. Of
most interest is the low-level dew point field, with an
arbitrarily critical value of 58-60F eroding enough surface-
based CIN to foster at least some surface-based convection. Will
need to closely monitor upstream trends over the next few
hours, with the greatest concern for convective segments
producing locally damaging winds and perhaps a brief tornado.

Beyond the evening convection, steeper low-level lapse rates
and lingering low-level moisture will actually result in the
potential for shallow surface-based showers/convection (no
lightning). While deep-layer forcing will be less favorable
under the deep dry slot aloft, cannot rule out some rotating
gusty showers ahead of the cold front.

Wind: Outside of any convection, south winds gusting to 30 mph
this afternoon will slightly back SSE while increasing this
evening, with some gusts in excess of 35 mph. After the main
convection clears the CWA toward midnight CST, the area will
remain fully in the warm sector for several hours overnight. A
small secondary 60-70 knot pre-frontal LLJ is expected to
develop over northern Illinois during this time as the mid-level
dry-slot takes hold over the area. Relatively steep low-level
lapse rates by nighttime standards should allow at least some
downward mixing of the stronger winds ahead of the front, with
strong CAA further enhancing mixing as the cold front sweeps
across the area late tonight. Meanwhile, an impressive
isallobaric wind component highlighted by 10mb/hr or more
pressure rises toward daybreak will provide added support for
stronger winds. Expectation is that WSW winds veering WNW will
gust 40 to 50 mph roughly in the 4 to 8am window, with the
potential for a few gusts nearing 60 mph. A short-fused Wind
Advisory may be needed if upstream observations early in the
morning favor gusts closer to 50 mph instead of 40 mph. Winds
will gradually veer N while diminishing mid-morning through the
afternoon.

Temps: With strong WAA now in place, temps have pushed into the
low 50s north to mid 50s south this afternoon. While precip may
temporarily stunt temps at times through this evening, they
should overall continue to rise to the mid 50s north to around
60 south. This will result in most locations ultimately
recording calendar day highs for both the 8th and 9th around
midnight. Temps will then fall through the 40s with the passage
of the cold front late tonight, with temps generally in the low
to mid 40s through the day Friday. Morning stratus should begin
to erode in the afternoon, but temps would underperform if
thicker stratus persists through the entire day.

Kluber


Friday night through Thursday:

Friday night into Saturday, a pair of upper-level waves -- one
initially over the southern Rockies/southern Plains and another
diving southeastward from Canada into the northern Plains --
will begin to phase over the Midwest. This phasing process will
yield a sprawling upper-level low over the region, which will
result in some showery periods in our area from Saturday morning
through Sunday morning. As is often the case with phasing
atmospheric waves (even just 36-48 hours out), some lingering
uncertainties remain, namely with respect to precipitation types
and the placement and magnitude of snow accumulations. However,
many other aspects of this weekend`s weather forecast are
becoming clearer as model data continues to converge on a common
solution.

The main wave of precipitation with this incoming system
appears that it will come Saturday morning as increasing DPVA
and upper-level diffluence tag team with low- to mid-level
frontogenesis to induce a southwest-to-northeast oriented band
of precipitation within an attendant baroclinic zone. Model
guidance remains mixed on exactly where the main axis of
precipitation will set up, but there is fair agreement across
the 12Z guidance suite that most or all of our forecast area
should see some sort of hydrometeors falling from the sky at
some point Saturday morning. With near-surface temperatures
expected to generally be in the low-mid 30s during this time,
precipitation types remain a big question mark for most of the
area. In general, though, rain will be more likely with
southeastward extent, snow will be more likely with
northwestward extent (and with time as a push of colder air
spreads into the area), and there will also likely be a
rain/snow mix line bisecting our CWA somewhere.

Where temperature profiles are cold enough (or dynamically cool
to a sufficient extent) to support outright snow, stout
frontogenetical forcing and 6-7C/km lapse rates through the
dendritic growth zone should allow for snow to fall at a fairly
steady clip within the heart of the snow band for up to 1-3
hours. Would not be surprised to see an axis of 1+"
accumulations get laid out somewhere across our CWA Saturday
morning with perhaps some slushy coatings occurring on some
roadways wherever the snow falls steadiest. Otherwise though,
lesser accumulations are expected, and the milder pavement
temperatures leading into the event should tend to keep
accumulations confined to grassy and colder surfaces.

Saturday afternoon into Saturday night, precipitation should
transition into isolated to scattered snow showers as cold air
advection steepens low- to mid-level lapse rates and the area
becomes engulfed underneath the core of the upper-level low.
Some additional dustings or coatings of snow could be observed
with the most robust snow showers during this time as falling
temperatures permit the snow to accumulate more easily, but this
should tend to be more localized in scope. Increasingly
blustery west-northwesterly winds during this time will also
make these snow showers efficient at reducing visibilities, so
motorists should plan on encountering sharply reduced
visibilities in spots.

The last push of snow shower activity may affect northeastern
portions of our forecast area Sunday morning, but otherwise,
drier air being advected in from the northwest should put an end
to the snow showers by Sunday afternoon. Temperatures in the
mid teens to mid 20s Sunday morning may not climb much during
the daytime on Sunday with the persisting blustery northwesterly
winds, but if skies manage to clear out quickly enough, then
some locations could still nevertheless see temperatures climb
above 30F during the afternoon.

Early next week, a predominantly northwesterly flow pattern is
expected to become established over the northern part of the
CONUS. This will allow for a few clipper-type disturbances to be
sent our way. The first of these disturbances looks to arrive
sometime Sunday night or Monday, though it does not appear that
it will saturate the tropospheric column enough for measurable
precipitation to be observed as it shoots southeastward through
the region. A better chance for precipitation should come with
a follow-up wave in the Tuesday-Wednesday time frame, with both
rain and snow appearing to be in play for precipitation types
with that. While temperatures should trend above normal Monday
into Tuesday, another cooldown is likely to occur in the wake of
this mid-week system.

Ogorek

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 534 PM CST Thu Jan 8 2026

Forecast concerns include...

Chance of thunderstorms this evening.
Mvfr cigs through Friday morning, ifr cigs this evening.
Strong/gusty southwest winds overnight/Friday morning.
Low level wind shear this evening.

Rain with embedded isolated thunderstorms will continue through
mid/late evening for the Chicago terminals with the rain slowly
ending from west to east by late evening. Satellite imagery
shows a dry/clear slot moving northeast through central MO into
far west central IL and this is expected to move across the
terminals in the late evening and early overnight hours. There
may be a few additional showers in the predawn hours as the main
cold front moves across the area.

Cigs have been slow to lower across the immediate Chicago
terminals but prevailing low mvfr cigs are expected with ifr
cigs possible with prevailing ifr cigs expected outside of the
Chicago metro area this evening. Cigs are expected to scattered
as the clear slot moves across the area and then mvfr cigs will
return overnight and continue through Friday morning, lifting
and scattering Friday afternoon.

Southeast winds will gust into the lower/mid 20kt range this
evening with some higher gusts possible with any thunderstorms.
Wind directions will turn to the south/southwest this evening
and then turn more to the southwest overnight when gusts are
expected to increase into the mid 30kt range. Some higher gusts
are possible with any showers that develop along/ahead of the
cold front in the predawn hours. Winds will turn northwest
Friday morning and steadily diminish into the afternoon,
becoming light north/northeast or variable Friday evening.

Low level winds will remain very strong this evening and even
with the expected surface gusts, low level wind shear will
continue this evening. cms

&&

.CLIMATE...
Issued at 254 PM CST Thu Jan 8 2026

Record warmth is forecast for Rockford and near record warmth for
Chicago today, January 8 and Friday, January 9. The high
temperature will likely occur around midnight between both
dates.

The record high and record warm low temperatures for both
Rockford and Chicago are included below:


                 Record Highs                Record Warm Lows

           January 8    January 9        January 8      January 9

Rockford:  55F (1965)   56F (2002)       36F (2008)     35F (2000)

Chicago:   63F (1965)   60F (1880)       45F (1876)     45F (1939)


NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 3 AM CST Friday for the IL and IN
     nearshore waters.

     Gale Warning from 3 AM to 9 AM CST Friday for the IL and IN
     nearshore waters.

     Small Craft Advisory from 9 AM to 3 PM CST Friday for Gary to
     Burns Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

Visit us at weather.gov/chicago